Bight stop mechanism for sewing machines

ABSTRACT

The present disclosure relates to zig-zag sewing machines including means for controlling the bight stops in order to produce ornamental patterns. In particular, the disclosure relates to electronically controlled sewing machines having storage means for storing stitch information and wherein logic means are used to select and release stitch information in timed relation with the operation of the sewing machine. The disclosure of the invention has particular application in those sewing situations wherein it is desired to use more than one needle in a single needle holder of the needle bar which therefore necessitates a limitation on the magnitude of the jogging or swinging of the needle bar in order to accommodate the multiple needles in the aperture of the needle plate. In accordance with the disclosure of the present invention whenever more than one needle is used in the sewing machine the electronic control of the bight stops is automatically put into effect whenever such multiple needle mode is selected.

BACKGROUND OF THE INVENTION

In sewing machines it is desirable in some sewing situations to be ableto use more than one needle as in the case, for example, of multicoloredembroidery stitching. When substituting two or more needles for a singleneedle in a zig-zag machine, it becomes necessary to limit the swingamplitude of the needles, or the bight stops, as the two or more needleswould swing in a wider path than a single needle which could take theneedles out of the area covered by the aperture in the needle plateresulting in a breaking of the needles during penetration of the fabric.It is known to limit the bight stops in mechanically controlled zig-zagmachines when substituting multiple needles for single needles, such asfor example shown in U.S. Pat. No. 3,296,987 granted Jan. 10, 1967. Insuch mechanically controlled machines the zig-zag motion is generallyimparted to the needle bar by a cam mechanism which is connected to theneedle bar mechanism through a cam follower and associated linkage. Inorder to adjust or limit the bight stops in such machines means aregenerally provided for altering the linkage between the cam mechanismand the needle bar mechanism.

In electronically controlled sewing machines of the type disclosed inco-pending U.S. patent application Ser. No. 431,649 .Iadd.(now patent#3,984,745) .Iaddend.filed on Jan. 8, 1974, cam mechanisms of the typementioned above are completely eliminated and logic means are used toselect and release stitch information stored in a memory means in timedrelation with the operation of the sewing machine. Digital informationfrom the memory means is converted to positional analog signals whichcontrol closed loop servo means including moving coil linear actuatorsdirectly controlling the position of conventional stitch forminginstrumentalities such as the zig-zag mechanism for the needle bar.Therefore it will be seen that in machines of this type means other thanthose which have been provided heretofore must be used for limiting thebight stops. What is required in order to limit the bight stops in anelectronically controlled machine is means for limiting the positionalanalog signals which control the closed loop servo means to therebyprovide a signal to said servo means which is reduced in proportion tothe reduction in swing amplitude or bight required for the situationwherein multiple needles or the like are used.

SUMMARY OF THE INVENTION

As briefly mentioned above, a machine of the type disclosed in thisinvention is controlled by electronic means including logic means whichselect and release stitch information from a stored memory in timedrelation with the operation of the sewing machine and in accordance witha pattern selected by the operator. The signal from the memory ispresented in digital form and is converted in a digital-to-analogconverter and through suitable amplification is fed to a moving coillinear actuator which directly controls the position of the needle barmechanism. A feedback circuit is also provided which senses the positionof the linear actuator in accordance with time and location and modifiesthe input signal so that the actuator will accurately assume theposition as called for by the original information released from thememory.

U.S. patent application Ser. No. 596,683 .Iadd.(now patent #4,016,821).Iaddend.filed July 16, 1975 discloses a means for overriding the analogsignal provided by the digital-to-analog converter for both feed andbight pattern information thereby providing a variable control of saidsignal to the linear actuator. Such a system is desirable for modifyingthe pattern information, as for example, to obtain an optimum buttonhole that would have a balanced appearance. However, it has been foundthat in situations where multiple needle use can be optionally selectedon the machine, fixed bight stop limits should be provided so as toprevent any possibility of needle breakage or the like. In accordancewith the present invention circuit means are provided which, whenselectively operational, impose a fixed limit on the analog signal atthe output of the digital-to-analog converter. Such fixed limit isimposed prior to input to the linear actuator and also prior to theoperation of any override controls, as described above, so that there isno danger in the operator modifying the signal with the override controlto cause the needles to swing a greater amplitude than is desired.

Accordingly, it is one object of the invention to provide a novel andimproved bight stop mechanism for a sewing machine.

It is another object of the invention to provide a novel and improvedbight stop mechanism for an electronically controlled sewing machine.

It is a further object of the invention to provide a novel and improvedbight stop mechanism for limiting the swing amplitude of the needle barin a zig-zag sewing machine when a multiple needle mode is selected.

Other objects and advantages of the invention will be best understoodwhen reading the following description with the accompanying drawings asidentified below.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a sewing machine showing fragmentedportions of the sewing instrumentalities and control mechanismsnecessary to illustrate the physical elements of the invention;

FIG. 2 is a general schematic block diagram for the bight control systemof the invention; and

FIG. 3 is a circuit diagram showing the bight control circuits of theinvention.

DESCRIPTION OF THE INVENTION

Referring to the drawings there is illustrated in FIG. 1, a sewingmachine, partially in phantom, including a frame 10 having a bed 12 anda bracket arm 14 supported in an overhanging relationship to the bed bya standard 16. The free end of the bracket arm 14 includes a headportion 18 in which is supported a needle bar gate 20 which in turnsupports a needle bar 22 for reciprocating motion in an endwisedirection in the usual manner as found in sewing machines. Endwisereciprocating motion is imparted to the needle bar 22 through suitableconnection with an arm shaft 24 driven in the conventional manner as byan electric motor or the like (not shown). A single needle or aplurality of needles 26, as illustrated are supported in the lowerextremity of the needle bar 22 and are disposed for cooperation beneaththe bed 12 with suitable sewing instrumentalities such as a looper (notshown) or the like.

As is known in zig-zag sewing machines, the needle bar gate 22 isoperatively associated with actuating mechanism for imparting lateraljogging motion to the needle bar 22, which, as illustrated in FIG. 1,includes a drive arm 28 pivotally connected to the needle bar gate asillustrated at 30. The drive arm 28 is operably connected to areversible linear motor or actuator 32 for imparting a linear motion tothe drive arm 28 and as a result jogging motion to the needle bar gate20 through the pivot connection 30. Reference may be made to U.S. patentapplication Ser. No. 431,649 filed on Jan. 8, 1974 and assigned to thesame assignee as the present invention for a more detailed descriptionof the linear actuator. Disposed within the bed 12 and below the needlebar 22 for operation in association therewith is a needle plate 34 whichincludes an aperture 36 having a width sufficient to at leastaccommodate a single needle during maximum width zig-zag motion.Supported beneath the bed plate 12 is a feed mechanism for feeding thework across the surface of the bed plate and includes a feed dog 38operably connected with suitable linkage generally indicated at 40 whichin turn is connected to a second linear motor or actuator 42. Asdescribed in co-pending application Ser. No. 596,683 filed July 16, 1975and assigned to the same assignee as the present invention, the feedmechanism is also electronically controlled so that electronic signalsare fed to the linear actuator 42 to position the feed mechanism for thedesired forward or reverse feed in accordance with a selected pattern.The feed mechanism itself forms no part of the present invention and forpurposes of the present invention other suitable feed mechanisms may beincorporated herein.

Referring to FIG. 2, illustrated therein is a schematic block diagramfor the bight control portion of the sewing machine. The feed controlportion is not illustrated and is essentially the same as the bightcontrol circuitry and reference to the bight control circuitryillustrated in FIG. 2 will be sufficient for purposes of understandingeither of the aforementioned control circuits. For a more detaileddescription of the feed control circuit reference may be made to theaforementioned U.S. patent application Ser. No. 596,683. As previouslymentioned, pattern information may be stored in a memory device which inthe present invention is incorporated in a MOSFET Large ScaleIntegration (LSI) integrated circuit designated at 44 in FIG. 2. Onemethod of extracting the information from the LSI 44 for presenting thesame to the digital-to-analog converter for bight and feed control isdisclosed in U.S. Pat. No. 3,855,956, assigned to the same assignee ofthe present invention. As disclosed therein digital information relatedto the positional coordinates for each stitch of a predetermined stitchpattern is stored in a static memory such as included in LSI 44. A pulsegenerator 46 (see also FIG. 1) is driven in timed relation with thesewing machine and produces a timing signal pulse between eachsuccessive stitch. The signal pulses are counted in a binary counter 48to provide a timed series of progressively increasing binary numberscorresponding to the progressively increasing number of stitches in thepattern. The output of the counter is applied as the address to thememory to recover as output therefrom the digital information related tothe positional coordinates for each stitch of the predetermined pattern.The memory output is applied to control driving devices operativelyconnected to impart a control range of movement to the needle and thefeed of the sewing machine to produce a specific predetermined positioncoordinate for the needle penetration during each stitch formation.

As further illustrated in FIG. 2, the pulses from the pulse generator 46are counted by binary counter 48 and presented at address input to theLSI 44. The LSI is illustrated in FIG. 1 as being mounted on a logicprinted circuit board 50. The output of the LSI 44 is presented asoutput digital information related to the positional coordinates foreach stitch in pulse width modulated form to digital-to-analog converter52 for the bight. The LSI 44 may also include a latch whereby the bightinformation may be held for timed release to the bight servo system at atime appropriate to the operation of the needle jogging mechanism in thestitching operation. Proper timing for the release of the bightinformation may be determined by the pulse generator 46.

The pulse width modulated signal presented along line 54 to thedigital-to-analog converter 52 is filtered, offset by rheostat 56 (FIG.3) and scaled by a voltage divider 58 in the converter in order toaccommodate a specific LSI 44 to those components between the LSI andthe load to account for manufacturing variability. Analog signals fromthe digital-to-analog converter 52 have an output on line 60 to a bightsignal control amplifier 62 which outputs on line 64 to the summingpoint 66 of a low level preamplifier 68 of a servo amplifier system.Further reference to the servo amplifier system may be found in theaforementioned U.S. patent application Ser. No. 431,649.

The output from the bight signal control amplifier 62 is also connectedby way of line 70 to FET 72 of the enhancement type, having its gateconnected by gate line 74 to the LSI 44. On suitable command the LSI 44will apply a gate voltage through a latch circuit to FET 72 by way ofgate line 74 thereby to place and retain FET 72 in the conductive or ONcondition. A feedback signal then passes through line 70 and FET 72 to awiper of a rheostat 78 supported on control block 76 (see FIGS. 1 and3).

Thus, the gain of the bight signal control amplifier 62 may becontrolled during pattern stitching or straight stitching through manualadjustment of the manual bight control rheostat 78. The manual bightcontrol rheostat 78 which as seen in FIG. 1 is adjusted by a knob 80 andis mounted on power supply and override printed circuit board 82.Energization of the circuitry to LSI 44 for applying a gate voltage toFET 72 may be accomplished by a proximity switch associated with knob 80and may be of the type described in co-pending U.S. patent applicationSer. No. 596,685, filed on July 16, 1975, entitled "Digital DifferentialCompacitance Proximity Switch" which is assigned to the same assignee asthe present invention. Rotation of knob 80 rotates wiper 84 of rheostat78 for adjustment of the bight control signal. Further details of theoverride arrangement may be had by referring to the aforementionedco-pending application Ser. No. 596,683, filed July 16, 1975. As alsomentioned in the co-pending application just referred to, overridecontrols may also be provided for the feed signals and to the balance ofthe feed and may be represented in the present application by knobs 86and 88 which respectively control balance and feed through suitablerheostats and circuitry similar to that described in relation to thebight control circuits above. For purposes of the present invention itneed only be understood that override circuit means may be provided formodifying the bight control signal after its amplification by bightsignal control amplifier 62.

As further illustrated in FIG. 3, the bight signal control amplifier 62is indicated as an operational amplifier with rheostat 78 providing thefeedback to the input. A MOSFET module 90, such as RCA type CD 4016A,comprises a plurality of dependent bilateral signal switches one ofwhich is switch 72. The module may also be mounted on a printed circuitboard 82 (see FIG. 1). As shown in the schematic of FIG. 3 a voltagesignal from LSI 44 on line 74 will place FET 72 in an ON condition,inserting the wiper 84 of rheostat 78 in by-pass arrangement in thefeedback circuit. Feedback resistance of the operational amplifier 62may thereby be reduced to decrease the gain of the operational amplifierand reduce the analog signal to the summing point 66 of the low levelpreamplifier 68 of the servo amplifier system mounted on servo circuitboard 92. Preamplifier 68 drives a power amplifier 94 which suppliesdirect current of reversible polarity to the electromechanical actuator32, which in the broadest sense comprises a reversible motor, toposition the actuator in accordance with the input analog voltage online 64. A feedback position senser 96 mechanically connected to thereversible motor 32 provides a feedback position signal on line 98indicative of the existing output position. The input analog voltage andthe feedback signal are algebraically summed at the summing point 66 tosupply an error signal on line 100. The feedback signal from theposition sensor is also differentiated with respect to time in adifferentiator 102 and the resulting rate signal is presented on line104 to the summing point 106 of the power amplifier 94 to modify thepositional signal at that point. The position sensor 96 may be anydevice that generates an analog voltage proportional to position and maybe a simple linear potentiometer connected to a stable reference voltageand functioning as a voltage divider. The differentiator 102 ispreferably an operational amplifier connected to produce an outputsignal equal to the time rate of change of the input voltage.

While the reversible motor 32 may be a conventional low-inertia rotaryd.c. motor, it is preferable, for purposes of the present invention thatit takes the form of a linear actuator in which a lightweight coil moveslinearly in a constant flux field and is directly coupled to the load tobe positioned. This simplifies the driving mechanical linkage andminimizes the load inertia of the system. A suitable power supplycircuit (not shown) may be connected to the AC house mains via atransformer for supplying 12 volt 60 hertz to the power supply. Thesupply, reduced to 12 volts a.c. undergoes full wave rectification, andfiltration to provide ± 15 VDC to the power amplifiers and also toprovide, through voltage regulators of a suitable type, ± 7.5 VDC in thebight position potentiometer 96 as well as ± 7.5 VDC to thedigital-to-analog offset voltage dividers in the digital-to-analogconverter 52. Although not shown, the power supply also provides ± 7.5VDC to LSI 44. As the power supply itself forms no part of the presentinvention, reference may be made to co-pending application Ser. No.596,683 mentioned above for a more detailed description of the typepower supply which may be used with the present invention. Also,reference may be made to the same co-pending application for a moredetailed description of the construction and operation of the LSIitself.

When sewing ornamental patterns, such as in embroidery stitching or thelike, wherein more than one color thread is desired, or in cases whereinparallel lines of ornamental stitches are desired, it is necessary tosubstitute a multiple needle holder for the single needle generally usedwith the machine. It will be readily apparent that when more than oneneedle is held in the needle bar, if the same swing amplitude or bightis used for zig-zag stitching as was in the case of a single needle, oneor both of the needles in the case of using two such needles may notalign itself with the needle plate aperture 36 during penetration of thefabric. Means must therefore be provided to insure that the swingamplitude or bight of the needles does not exceed the width of theneedle plate aperture. In accordance with the present inventionadditional circuit means are provided for modifying the electronicpattern control signal for the bight so that when the machine is in amultiple needle mode the maximum bight will be automatically reduced inproportion to the number of needles carried by the needle bar.

Referring to FIGS. 1, 2 and 3, a switch 110 is carried by control panel76 and has its contacts in parallel through lines 112 and 114 with theoutput line 60 of the digital-to-analog converter 52. .Iadd.Preferably,the circuit is arranged such that when the switch 110 is open, the bightwill be reduced for multiple needle sewing, and when the switch 110 isclosed, a wider bight will be available for single needle sewing..Iaddend.It will be recalled, as discussed above, the digital-to-analogconverter 52 puts out an analog signal which is converted from thedigital information from the memory to provide a control signal for thebight in accordance with a selected pattern. In order to reduce thesignal from the digital-to-analog converter 52, a fixed resistance inthe form of a resistor 116 is placed in line 114 which resistor 116 hasa resistance selected so that it will reduce the analog voltage from thedigital-to-analog converter in an amount proportion to the number ofneedles, which in the case of switch 110 and its associated circuit inthe preferred embodiment illustrated is selected for twin or two needlesewing. Thus, for example, the resistance of resistor 116 may be such to.[.reduce.]. .Iadd.influence .Iaddend.the output from thedigital-to-analog converter by an amount of 50%. It will be further seenthat the parallel circuit containing switch 110 and resistor 116 isinserted into the circuitry prior to the application of any override orfeedback signals, as would appear on line 70 subsequent to amplificationof the bight control signal through bight signal control amplifier 62.Therefore, .[.when the switch 110 is closed to insert the resistance 116into the circuit.]. any modification of the signal thereafter as throughthe override controls or the feedback .[.would only.]. .Iadd.could not.Iaddend.have an effect on .[.a reduced.]. .Iadd.the maximum.Iaddend.value .Iadd.of the .Iaddend.control signal. By this means anymodification of the bight control signal would not give rise to anyconcern that the swing amplitude of the needles would exceed the widthof the needle plate aperture 36. It will also be understood, thatinstead of a single position switch 110 a multiple position switch maybe provided wherein multiples of resistance may be inserted into thecircuit in the same manner as the resistor 116 for situations whereinmore than two needles will be used in the needle bar.

It will be seen from the above description that a novel and improvedbight stop control mechanism is provided for a sewing machine forlimiting the swing amplitude of a needle bar during zig-zag stitchingwhen more than one needle is present in the needle bar. In particular,means are provided for modifying electronic bight control signals whenthe sewing machine is placed in a multiple needle mode to limit theswing amplitude of the needle bar so as to prevent any damage to theneedles or the work or other elements of the sewing machine. While theinvention has been described in its preferred embodiments, it will beobvious to one skilled in the art that various changes and modificationsmay be made therein without departing from the spirit and scope of theappended claims.

Having thus described the nature of the invention, what we claim hereinis:
 1. In a sewing machine having endwise reciprocable needle means,jogging means for initiating relative lateral movement of said needlemeans, electric motor means connected to said jogging means such thatinitiation of the relative lateral movement of said needle means iscontrolled in accordance with movement of said electric motor means,means including first circuit means for generating electrical inputsignals in accordance with predetermined stitches in a selected patternand for connecting said electrical input signals to said electric motormeans, said electric motor means having a work output proportional tosaid electric input signals, and circuit means in addition to said firstcircuit means and including switch means for limiting the magnitude ofthe electrical input signals to said electric motor means, said circuitmeans being operative for reducing said electrical input signals a fixedpercentage each time said switch is actuated whereby upon actuation ofsaid switch means the maximum extent of lateral movement of said needlemeans will be limited.
 2. In a sewing machine as recited in claim 1further comprising override control means for selectively varying themagnitude of said electrical input signals, and said circuit means beingoperative to reduce said electrical input signals a fixed percentageirrespective of the selection of said override control means.
 3. In asewing machine as recited in claim 2 wherein said circuit means isoperative for reducing said electrical input signals prior to anyvariation of said electrical input signals by said override controlmeans.
 4. In a sewing machine as recited in claim 1 wherein saidelectrical motor means comprises a reversible electric motor, saidreversible electric motor being responsive to said electrical inputsignals for initiating relative lateral movement of said jogging meansin first and second directions.
 5. In a sewing machine as recited inclaim 4 wherein said reversible electric motor comprises a linear motor.6. In a sewing machine having a needle bar disposed for endwisereciprocation, said needle bar being adapted for supporting one or moreneedles for reciprocation therewith, jogging means responsive toelectrical input signals for initiating lateral movement of said needlebar to produce patterned stitches with the magnitude of lateral movementof said needle bar being proportional to the magnitude of the electricinput signals, pattern control means including first circuit meansoperative for supplying electrical input signals of predeterminedmagnitude to said jogging means, and circuit means in addition to saidfirst circuit means and including switch means operatively connected tosaid pattern control means, said switch means being adapted foroperation when more than one needle is supported by said needle bar forreducing the predetermined magnitude of the electrical input signals afixed percentage of its original value supplied by said pattern controlmeans.
 7. In a sewing machine as recited in claim 6 wherein said circuitmeans includes resistance means, the value of said resistance meansbeing selected in accordance with the number of needles supported bysaid needle bar.